net: throw on invalid socket timeouts

This commit restricts socket timeouts non-negative, finite
numbers. Any other value throws a TypeError or RangeError.
This prevents subtle bugs that can happen due to type
coercion.

Fixes: https://github.com/joyent/node/issues/8618
PR-URL: https://github.com/joyent/node/pull/8884


Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Timothy J Fontaine <tjfontaine@gmail.com>